Basic differences in the immune response of atopic and non-atopic individuals to antigens administered via the respiratory route will be studied. We will attempt to demonstrate possible differences in specific local secretory IgA and IgE "primary" responses of atopic and non-atopic individuals to previously unencountered antigens administered via the nasal mucous membrane route. The extent and distribution of IgE and IgA producing lymphoid cells in respiratory tract mucosal tissue of atopic and non-atopic individuals, as well as possible quantitative, developmental, or functional differences in secretory IgA will be investigated. In addition to the above studies, we will also investigate the immunologic mechanisms involved in hypersensitivity pneumonitis. Experimental animal models will be developed to determine the role of sensitive lymphocytes and macrophages in the production of lung pathology. Thermophilic actinomycete antigens which are important etiologic agents in these diseases will also be identified.